Vibration force generator

ABSTRACT

A reaction-type vibration generator which includes, generally, a housing having therein two fixed shafts which are geared together so that they rotate synchronously in opposite directions. Each of these two fixed shafts having an eccentric mass affixed to it, which mass comprises a portion one-half of the total mass rotated by that shaft. These shafts each further have a sleeve disposed concentrically about it, and these sleeves each support the other portion (one-half) of the total mass rotated by the individual shafts. The sleeves further are keyed to the shafts by means of a pair of toothed gears affixed to the shafts and to the sleeves, respectively, in a fashion such that the assembly can be easily loosened, the sleeves angularly rotatably displaced with respect to the shafts to vary the net unbalanced mass to, in turn, vary the amplitude of vibration of the vibration generator, and then fixedly keyed together again so that the masses affixed to the fixed shafts and to the sleeves rotate in synchronism. Scale means are associated with each shaft and sleeve combination, to accurately establish the desired amplitude of vibration.

I Umte d States Patent 51 3,640,508

Reibig [451 Feb. 8, 1972 [54] VIBRATION FORCE GENERATOR Pn'maryExaminer-Dave W. Arola [72] Inventor: Eric A. Reibig, Waukegan, lll.Ammey- Dmlmk Knechtel & Godula [73] Assignee: All American Tool 8: Mfg.Co., Skokie, Ill. [57] ABSTRACT [22] Filed: June 25, 1969 Areaction-type vibration generator which includes, generally, a housinghaving therein two fixed shafts which are geared [2]] Appl' 836534together so that they rotate synchronously in opposite directions. Eachof these two fixed shafts having an eccentric [52] 0.8. CI. ..259/72,74/87 mass f i to i whi h m mprises a portion one-half of [51] Int. Cl.30 9/00 the total mass rotated by that shaft. These shafts each further[58] Field of Search ..259/12, 29, 54, 72, 173, DlG. 42, have a Sleevedisposed concentrically about and these 259/1 74/37 sleeves each supportthe other portion (one-half) of the total mass rotated by the individualshafis. The sleeves further are [56] References Cited keyed to theshafts by means of a pair of toothed gears aflixed to the shafts and tothe sleeves, respectively, in a fashion such UNITED STATES PATENTS thatthe assembly can be easily loosened, the sleeves angularly rotatablydisplaced with respect to the shafts to vary the net 3 22;? unbalancedmass to, in turn, vary the amplitude of vibration of 327773l 10/1966Pinson "31G 42 the vibration generator, and then fixedly keyed togetheragain so that the masses affixed to the fixed shafts and to the sleevesFOREIGN PATENTS OR APPLICATIONS rotate in synchronism. Scale means areassociated 'with each shaft and sleeve combination, to accuratelyestablish the 894,514 3/ 1944 France....-. ..258/DIG. 42 desiredamplitude of vibration 1,213,355 3/1966 Germany ..259/DIG. 42

10 Claims, 9 Drawing Figures T. e I 1 60 l I e V M PMENIEBFEB 8 I9723,60. 508

SHEET 1 OF 3 INVENTOR Eric A. Reibig 3% fia /x am ATTYS.

PAIENIEUHB 8 1912 3. 840,508

SHEET 2 OF 3 5 v INVENTOR Eric A. Reibfg BY fiMJ fieI/ QW ATTYS.

PAIENTEDFEB 8 I972 QfififiQ mm 3 a 3 LLILILLI FIG. 6 FIG. I

FIG. 8 FIG. 9

INVENTOR Eric A. Reibig ATTYS.

VIBRATION FORCE GENERATOR This invention relates to an improvedreaction-type vibration generator.

Every mechanical assembly contains pans possessing mass supported bymembers possessing elasticity, and all such combinations have a naturalperiod of vibration. If they are forced to vibrate at the frequency oftheir natural period, they may move over a large amplitude with theapplication of relatively little energy. Such resonant conditions oftenoccur at unexpected places, and unless tests are made to determine andeliminate these conditions, destructive stresses may result, terminatingin fractures, breaks or other failures. Components of aircraft,automotive, marine craft and certain industrial and domestic equipmentmust be tested under conditions of vibration more stringent than areencountered in service to insure against failure, for their continuedoperation under all conditions is of vital importance.

One manner in which various articles of this type are tested is by meansof a vibration fatigue testing machine. These machines normally includea freely suspended table to which the articles can be securely afiixed,and a vibration generator usually is affixed to and adapted to vibrateboth the table and the article, over a wide frequency range and atdifferent amplitudes of vibration. Reaction-type vibration generatorshave been used for some time in these machines, to vibrate the tablethereof, since they probably form the simplest and most sturdy equipmentfor producing vibrations.

The simplest reaction-type vibration generator consists of a housingcarrying a shaft on which is mounted an eccentric mass. The housing isaffixed to the table of the fatigue testing machine, and when the shaftis rotated, the centrifugal force of the unbalanced mass createsreactions against the housing having a tendency to move the house, andhence the table, in an opposite direction at any point during completerotation. In those cases where vibrations which are linear and followthe law of harmonic motion are desired, the vibration generators usuallyinclude within the housing two oppositely rotating shafts withunbalanced mass which are geared together so that they rotatesynchronously in opposite directions.

It is generally well known that the amount of vibration amplitudeproduced by this type of vibration generator is given by the equation:

small mass radius of gyration amplitude large mass vibration In order tobe able to control amplitudes at will, many of the vibration generatorsinclude a provision for either changing the radius of gyration of theunbalanced mass or for varying the net unbalanced mass. The latterdesign is probably more commonly used than the former, and usually splitmasses are provided so that the net unbalanced mass can be varied byphysically angularly displacing on the shaft or shafts one portion ofthe mass with respect to the other.

Physically angularly displacing one portion of the mass with respect tothe other on the shaft is generally a relatively difficult andtime-consuming task. This is due to the fact that the masses are affixedto the shaft or shafts and, furthermore, are enclosed within thehousing. The latter, in most cases, in addition, is affixed to theunderside of the table of the vibration fatigue testing machine, withinan enclosure. Accordingly, in order to physically angularly displace thesplit masses with respect to one another to vary the amplitude ofvibration, the whole machine has to be disassembled just to gain accessto the split masses. It therefore would be extremely advantageous ifsome relatively simple arrangement is provided to angularly adjustablyposition the split masses, so that the amplitude of vibration can beeasily and quickly varied, to eliminate the need to disassemble themachine which, of course, would substantially reduce the downtime of themachine.

Accordingly, it is an object of the present invention to provid 2improved reactiontype vibration generators.

More specifically, an object is to provide improved reaction-typevibration generators having provisions whereby the amplitude ofvibration thereof can be easily and quickly variably adjusted.

A still further object is to provide improved reaction-type vibrationgenerators having provisions whereby the amplitude of vibration thereofcan be easily and quickly variably adjusted, without the necessity ofdisassembling it as in the past and without the need of any specialtools.

Still another object is to provide improved reaction-type vibrationgenerators of the above-described type constructed in a fashion suchthat the amplitude of vibration thereof can be variably adjusted inexact increments, from a maximum to a minimum value.

Still another object is to provide improved reaction-type vibrationgenerators of the above-described type constructed in a fashion such asto maintain amplitudes substantially constant once adjusted to thedesired amplitude of vibration.

A still further object is to provide improved reaction-type vibrationgenerators of the above-described type which are relatively simple inconstruction and are substantially maintenance free in comparison tomost presently available (onehalf) portion (one-half) vibrationgenerators which likewise have provisions for adjusting the amplitude ofvibration thereof.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The above objectives are accomplished with a reaction-type vibrationgenerator which includes, generally, a housing having therein two fixedshafts which are geared together so that they rotate synchronously inopposite directions. Each of these two fixed shafts having an eccentricmass affixed to it, which mass comprises a portion lof the total massrotated by that shaft. These shafts each further have a sleeve disposedconcentrically about it, and these sleeves each support the otherportion (one-half of the total mass rotated by the individual shafts.The sleeves further are keyed to the shafts by means of a pair oftoothed gears affixed to the shafts and to the sleeves, respectively, ina fashion such that the assembly can be easily loosened, the sleevesangularly rotatably displaced with respect to the shafts to vary the netunbalanced mass to, in turn, vary the amplitude of vibration of thevibration generator, and then fixedly keyed together again so that themasses affixed to the fixed shafts and to the sleeves rotate insynchronism. Scale means are associated with each shaft and sleevecombination, to accurately establish the desired amplitude of vibration.

The invention accordingly comprises the features of construction,combination of elements, and arrangements of parts which will beexemplified in the construction hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings in which:

FIG. 1 is a perspective view of a vibration generator exemplary of thepresent invention, affixed to the underside of the table of a vibrationfatigue testing machine;

FIGS. 24 are views generally illustrating the manner in which theeccentric masses enclosed within the housing of the vibration generatorare angularly adjustably positioned to vary the amplitude of vibrationof the vibration generator;

FIG. 5 is a top plan view, partially sectionalized, of the vibrationgenerator;

FIG. 6 is a partial view of the vibration generator illustrating theconstruction of the adjusting assembly thereof, the latter beingsectionalized and illustrated in its locked position;

FIG. 7 is a view like FIG. 6, however, illustrating the adjustingassembly in its unlocked position so as to permit the eccentric massesto be angularly adjustably positioned with respect to one another;

FIG. 8 is a sectional view taken along lines 8-8 of FIG. 7; and

FIG. 9 is a sectional view taken along lines 99 of FIG. 7.

Similar reference characters refer to similar parts throughout theseveral views of the drawings.

Referring now to the drawings, in FIG. 1 there is illustrated avibration generator 10 exemplary of the present invention affixed to theunderside of table 11 which may be, for example, the table of avibration fatigue testing machine (not shown). The vibration generator10 is easily affixed to the table 11 by means of threaded screws 18extended through a peripheral flange 19 integrally formed with thehousing 12 of the vibration generator. Aff'ixed beneath the vibrationgenerator 10 is a motor 16 which is coupled to and adapted to rotate adrive shaft 14, in a manner described more fully below. The drive shaft14, in turn, is geared to and rotates an idler shaft 15. Eccentricmasses, 34, 35 and 36, 37 are affixed to the drive shaft 14 and theidler shaft 15, respectively (see FIG.

and when the drive shaft and the idler shaft are rotated, thecentrifugal force of the eccentric weights, when unbalanced, createsreactions against the housing 12 of the vibration generator having atendency to move the housing, and hence the table 11, in an oppositedirection at any point during complete rotation. This operation of areaction-type vibration generator such as the vibration generator 10 isgenerally well known.

As can be'best seen in FIG. 5, the drive shaft 14 is rotatably andfixedly supported by means of a bearing 21 retained within a gearhousing 23 removably affixed to the housing 12 and by means of bearings22 and 24 affixed to the housing 12. The drive shaft 14 has a V-beltpulley or a timing belt pulley (not shown) affixed to its one end whichis coupled to and driven by means of the motor 16, to rotate the driveshaft 14. The motor 16 preferably is a variable speed motor so that thevibration generator 10 can be operated over a wide frequency range. Thegear housing 23 is removably affixed to the housing 12 by means ofthreaded screws 26 so that the gear housing 23 can be easily removed toinspect the spiral gears 28 and 30 protectively enclosed therein.

The idler shaft is rotatably supported within the housing 12 by means ofbearings like the bearings 22 and 24, and in generally the same fashion.It may be noted, however, that the left end (as illustrated) of theidler shaft 15 need not project out of the gear housing 23, as in thecase of the drive shaft 14. The spiral gear 28 is fixedly secured to thedrive shaft 14 by means of a taper pin (not shown) extended through thespiral gear hub 29 and furthermore, is meshed with and drives the spiralgear 30. The spiral gear 30 likewise is fixedly secured to the idlershaft 15 by means of a taper pin 31 extended through its hub and theidler shaft 15. It may be noted that, with this arrangement, the idlershaft 15 is rotated in a direction opposite to the direction of rotationof the drive shaft 14, when the latter is rotatably driven by means ofthe motor 16.

The eccentric weights 34 and 35, as can be best seen in FIGS. 2-4, eachare semicircular in shape, as are the eccentric weights 36 and 37. Theeccentric weight 34 is fixedly secured to an enlarged diameter portion32 of the drive shaft 14 by means of a generally U-shaped clamp 38, soas to be eccentrically affixed to the drive shaft 14, in the manner bestshown in FIGS. 2-4. It may be noted that the eccentric weight 34 and theclamp 38 are affixed to the drive shaft 14 by means of threaded bolts 64so that the eccentric weight can be easily removed and replaced by meansof, for example, an eccentric weight of a greater mass so that themaximum vibration amplitude of the vibration generator 10 can beincreased or decreased.

The eccentric mass 35 is affixed in a similar fashion, that is, by meansof a clamp 38, to a short sleeve 40 which is concentrically androtatably disposed about the drive shaft 14. The outer diameter of theshort sleeve 40 corresponds to the diameter of the large diameterportion 32 of the drive shaft 14 so that the eccentric weights 34 and 35are of the same radius, as can be best seen in FIG. 2.

An adjusting dial 44 is concentrically disposed about the end of theshort sleeve 40, exteriorly of the housing 12 of the vibration generator10, and is keyed to and rotatable with the Slit rt sleeve 40, by meansof a key 42.

A clutch 46 is concentrically disposed about the end of the drive shaft14 and is fixedly secured to the latter so as to be rotatable with it,by means of a key 43. The mating faces of the adjusting dial 44 keyed tothe short sleeve 40 and the clutch 46 keyed to the drive shaft 14 haveteeth 51 on them which are adapted to meshingly engage to lockinglyaffix the adjusting dial 44 and the clutch 46 together. The teeth 51 onthe adjusting dial 44 and the clutch 46 are maintained meshed togetherby means of a locknut 48 threadedly affixed to the threaded end portion50 on the drive shaft 14. As can be seen, by threadedly tightening thelocknut 48, the latter abuts against the clutch 46 to forcibly urge theteeth thereon in meshing engagement with the teeth on the adjusting dial44. Accordingly, it can be seen that with this arrangement. the shortsleeve 44 with the eccentric weight 35 affixed to it is caused to rotatealong with the drive shaft 14 and the eccentric weight 34 affixedthereto.

A short sleeve 40 is positionably affixed on the drive shaft 14 by meansof a lockring 60. Also, a spacer ring 61 is disposed between the bearing22 and the adjusting dial 44 to positionably space the latter.

The eccentric weight 36 is replaceably fixedly secured to an enlargeddiameter portion 39 of the idler shaft 15 by means of a clamp 38. Theeccentric weight 37 similarly is fixedly secured to a sleeve 41 which isconcentrically disposed about and rotatable on the idler shaft 15. Thissleeve 41 has a diame ter corresponding to the diameter of the largediameter portion 39 of the idler shaft 15 so that the eccentric weights36 and 37 are of the same radius, as in the case of the eccentricweights 34 and 35 affixed to the drive shaft 14 and the short sleeve 40,respectively. It may be noted that the eccentric weights 36 and 37 aredisposed closely together and are spaced between the eccentric weights34 and 35.

An adjusting dial 45 is keyed to the sleeve 41 and a clutch 47 is keyedto the idler shaft 15, in the same manner as described above in the caseof the adjusting dial 44 and the clutch 46. The adjusting dial 45 andthe clutch 47 likewise have teeth 51 on the mating surfaces thereof, anda locknut 49 is threadedly affixed to the end of the idler shaft 15 andis adapted to meshingly engage the teeth 51 on the adjusting dial 45 andthe clutch 47, as in the case of the locknut 48. Accordingly, in thiscase also, the sleeve 41 with the eccentric weight 37 affixed to itrotates with the idler shaft 15 having the eccentric weight 36 affixedthereto.

As indicated above, in order to be able to control the amplitude ofvibration of reaction-type generators, many of the vibration generatorsinclude a provision for either changing the radius of gyration of theunbalanced mass or for varying the net unbalanced mass. In the instantcase, the amplitude of vibration of the vibration generator 10 iscontrolled by varying the net unbalanced mass, by physically angularlydisplacing the eccentric weight 34 with respect to the eccentric weight35, and by physically angularly displacing the eccentric weight 36 withrespect to the eccentric weight 37. The angular displacement between theeccentric weights 34 and 35 and between the eccentric weights 36 and 37,of course, must be the same in order to provide vibrations which arelinear and follow the law of harmonic motion. Furthermore, as indicatedabove, prior to the advent of the present invention, physicallyangularly displacing the eccentric weights with respect to each other isa relatively difficult and timeconsuming task. This is due to the factthat the vibration generator normally had to be physically removed frombeneath the table of the vibration fatigue testing machine in order togain access to the eccentric weights closed within the housing so thatthe weights could be loosened and repositioned on the shaft or shaftswithin the housing. With the above-described arrangement andconstruction of the vibration generator 10, physically angularlydisplacing the eccentric weights to vary the amplitude of vibration ofthe vibration generator 10 can be easily and quickly accomplished,without the necessity of removing the housing 12 from the table 11 orotherwise disassembling the vibration generator.

This is accomplished in the following manner. in order to physicallyangularly displace the eccentric weight 34 with respect to the eccentricweight 35, the locknut 48 first is loosened. Thereafter, the clutch 46is slidably displaced on the drive shaft 14 to disengage the teeth onthe clutch 46 and the adjusting dial 44, as illustrated in FIG. 7.Preferably, a number of springs 54 (four as illustrated) are disposedwithin cavities 55 positionably spaced about the diameter of the clutch46, so that the springs bear against the adjusting dial 44 to bias theclutch 46 outwardly on the drive shaft 14 and against the locknut 48.Therefore, when the locknut 48 is loosened, the teeth 51 on the clutch46 are automatically disengaged with the teeth on the adjusting dial 44.With the teeth 51 disengaged, the drive shaft 14, for example, can beheld fixed by gripping the clutch 46 and the sleeve 40 angularlyrotatably displaced with respect to it, by gripping and rotating theadjusting dial 44. The clutch 46 has an index marker or pointer 56 (FIG.2) affixed to it and this index marker functions in conjunction with thedisplacement scale 52 on the adjusting dial 44, to visually indicate therelationship of the eccentric weights 34 and 35 with respect to oneanother, as more fully described below.

In HO. 2, it can be seen that the index marker 56 is aligned with thezero indicia on the displacement scale 52. With this setting, theeccentric weights 34 and 35 are diametrically disposed with respect toone another, as illustrated, and the amplitude of vibration will bezero. In FIG. 4, the index marker 56 is aligned with the indicia on thedisplacement scale 52, and the eccentric weights 34 and 35 are angularlyaligned so that the total mass thereof is eccentrically disposed on oneside of the drive shaft 14. In this position, he amplitude of vibrationof the vibration generator 10 will be at a maximum value. The remainingindicia on the displacement scale 52 is calibrated in a fashion suchthat the amplitude of vibration can be varied in tenths, from a minimumto a maximum value. For example, as illustrated in FIG. 3, the indexmarker 56 is aligned with the indicia 5 of the displacement scale, andthe eccentric weights 34 and 35 are angularly displaced with respect toone another such that the amplitude of vibration of the vibrationgenerator 10 will be 50 percent of the maximum possible amplitude ofvibration.

The eccentric weights 37 and 38, of course, are angularly adjustablydisplaced with respect to one another, in an amount equal to the angulardisplacement of the eccentric weights 34 and 35. In other words, if theindex marker 56 is aligned with the indicia 5 on the displacement scale52, the index marker affixed to the clutch 47 must be likewise alignedwith the indicia 5 on the displacement scale affixed to the adjustingdial 45.

From the above description, it can be seen that the two pairs ofeccentric weights 34, 35 and 37, 38 can be easily and quickly angularlyadjustably positioned so as to vary the amplitude of vibration of thevibration generator 10. Furthermore, the amplitude of vibration can bevaried, without the necessity of removing the vibration generator andphysically disassembling and displacing them. The adjusting scales andthe index markers associated with the adjusting dials and the clutchalso permit the amplitude of vibration to be adjusted in a known manner.

The locknuts 48 and 49, the clutches 46 and 47 and the adjusting dials44 and 45 all preferably have a number of recessed cavities 62 providedin them, for receiving the ends of a pair of lever bars (not shown).These lever bars are advantageously used to facilitate loosening andtightening the locknuts 48 and 49 since the latter should be securelytightened against the clutches 46 and 47. This, of course, isaccomplished by extending one end of the lever bars in the cavities 62in the locknut and in the clutch, respectively, and exerting oppositerotational forces on the lever bar to loosen or tighten the locknut.Thereafter, the lever bar is removed from the locknut and inserted inthe cavity 62 in the adjusting dial, to assist in angularly rotating onepair of the eccentric weights witi. respect to one another.

ciently attained and certain changes may be made in the aboveconstruction. Accordingly, it is intended that all matter contained inthe above description or shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

Now that the invention has been described, what is claimed as new anddesired to be secured by Letters Patent is:

l. A reaction-type vibration generator comprising a housing; at leastone shaft having a mass eccentrically secured thereto rotatablysupported within said housing; a sleeve concentrically disposed aboutsaid shaft and having a like mass eccentrically secured thereto in alike fashion; a locking mechanism comprising first lock means fixedlysecured to said sleeve and second lock means fixedly secured to saidshaft, said first and second lock means being releasably locked togetherto cause said shaft and said sleeve to rotate together as a unit, andbeing adapted to be unlocked to permit said shaft and said sleeve to berotated with respect to one another to angularly adjustably positionsaid masses affixed thereto with respect to one another to vary theamplitude of vibration of said vibration generator.

2. The reaction-type vibrator generator of claim 1, wherein said firstlock means comprises an adjusting dial and said second lock meanscomprises a clutch, the mating faces of said adjusting dial and saidclutch having a plurality of teeth thereon which meshingly engage toreleasably lock said adjusting dial and said clutch together to causesaid shaft and said sleeve to rotate together as a unit.

3. The reaction-type generator of claim 2, further including a locknutthreadedly affixed to said shaft so as to engage and forcibly urge saidclutch in engagement with the adjusting dial affixed to the sleeveconcentrically disposed about it, to meshingly engage the teeth thereonto releasably lock said adjusting dial and said clutch together.

4. The reaction-type vibrator f claim 3, wherein biasing means areaffixed to one of said adjusting dial and said clutch for biasing saidclutch out of engagement with said adjusting dial, whereby said clutchand said adjusting dial are automatically disengaged when said locknutis loosened.

5. The reaction-type vibration generator of claim 3, wherein saidadjusting dial has a displacement scale affixed to it and said clutchhas an index marker afiixed to it, said displacement scale and saidindex marker being affixed thereto and calibrated in a fashion such thatthe amplitude of vibration of said vibration generator can be adjustedby aligning said index marker with corresponding indicia on saiddisplacement scale.

6. A reaction-type vibration generator comprising a housing; a pair ofshafts each having a mass eccentrically secured thereto rotatablysupported within said housing and adapted to be rotated in oppositedirections in synchronism; a sleeve concentrically disposed about eachof said shafts and having a like mass eccentrically secured thereto in alike fashion; a locking mechanism associated with each of said shafts,said locking mechanisms each comprising first lock means fixedly securedrespectively to one of said sleeves and second lock means fixedlysecured to the associated one of said shafts, said first and second lockmeans being releasably locked together to cause said shaft and saidsleeve associated with it to rotate together as a unit, and beingadapted to be unlocked to permit said shaft and said sleeve to berotated with respect to one another to angularly adjustably positionsaid masses affixed thereto with respect to one another to vary theamplitude of vibration of said vibration generator.

7. The reaction-type vibration generator of claim 6, wherein each ofsaid first lock means comprises an adjusting dial and each of saidsecond lock means comprises a clutch, the mating faces of said adjustingdials and said clutches having a plurality o teeth thereon whichmeshingly engage to releasably lock said adjusting dials and saidclutches together to cause said shafts and said sleeves with which theyare respectively associated to rotate together as a unit.

8. The reaction-type generator of claim 7, further including a locknutthreadedly affixed to each of said shafts so as to engage and forciblyurge the clutch associated with that shaft in engagement with theadjusting dial affixed to the sleeve concentrically disposed about it,to meshingly engage the teeth thereon to releasably lock said adjustingdial and said clutch together.

9. The reaction-type vibrator of claim 8, wherein biasing 7 means areaffixed to each associated pair of adjusting dials and clutches forbiasing said clutch out of engagement with said adjusting dial, wherebysaid clutches and said adjusting dials locknuts are

1. A reaction-type vibration generator comprising a housing; at leastone shaft having a mass eccentrically secured thereto rotatablysupported within said housing; a sleeve concentrically disposed aboutsaid shaft and having a like mass eccentrically secured thereto in alike fashion; a locking mechanism comprising first lock means fixedlysecured to said sleeve and second lock means fixedly secured to saidshaft, said first and second lock means being releasably locked togetherto cause said shaft and said sleeve to rotate together as a unit, andbeing adapted to be unlocked to permit said shaft and said sleeve to berotated with respect to one another to angularly adjustably positionsaid masses affixed thereto with respect to one another to vary theamplitude of vibration of said vibration generator.
 2. The reaction-typevibrator generator of claim 1, wherein said first lock means comprisesan adjusting dial and said second lock means comprises a clutch, themating faces of said adjusting dial and said clutch having a pluralityof teeth thereon which meshingly engage to releasably lock saidadjusting dial and said clutch together to cause said shaft and saidsleeve to rotate together as a unit.
 3. The reaction-type generator ofclaim 2, further including a locknut threadedly affixed to said shaft soas to engage and forcibly urge said clutch in engagement with theadjusting dial affixed to the sleeve concentrically disposed about it,to meshingly engage the teeth thereon to releasably lock said adjustingdial and said clutch together.
 4. The reaction-type vibrator of claim 3,wherein biasing means are affixed to one of said adjusting dial and saidclutch for biasing said clutch out of engagement with said adjustingdial, whereby said clutch and said adjusting dial are automaticallydisengaged when said locknut is loosened.
 5. The reaction-type vibrationgenerator of claim 3, wherein said adjusting dial has a displacementscale affixed to it and said clutch has an index marker affixed to it,said displacement scale and said index marker being affixed thereto andcalibrated in a fashion such that the amplitude of vibration of saidvibration generator can be adjusted by aligning said index marker withcorresponding indicia on said displacement scale.
 6. A reaction-typevibration generator comprising a housing; a pair of shafts each having amass eccentrically secured thereto rotatably supported within saidhousing and adapted to be rotated in opposite directions in synchronism;a sleeve concentrically disposed about each of said shafts and having alike mass eccentrically secured thereto in a like fashion; a lockingmechanism associated with each of said shafts, said locking mechanismseach comprising first lock means fixedly secured respectively to one ofsaid sleeves and second lock means fixedly secured to the associated oneof said shafts, said first and second lock means being releasably lockedtogether to cause said shaft and said sleeve associated with it torotate together as a unit, and being adapted to be unlocked to permitsaid shaft and said sleeve to be rotated with respect to one another toangularly adjustably position said masses affixed thereto with respectto one another to vary the amplitude of vibration of said vibrationgenerator.
 7. The reaction-type vibration generator of claim 6, whereineach of said first lock means comprises an adjusting dial and each ofsaid second lock means comprises a clutch, the mating faces of saidadjusting dials and said clutches having a plurality of teeth thereonwhich meshingly engage to releasably lock said adjusting dials and saidclutches together to cause said shafts and said sleeves with which theyare respectively associated to rotate together as a unit.
 8. Thereaction-type generator of claim 7, further including a locknutthreadedly affixed to each of said shafts so as to engage and forciblyurge the clutch associated with that shaft in engagement with theadjusting dial affixed to the sleeve concentrically disposed about it,to meshingly engage the teeth thereon to releasably lock said adjustingdial and said clutch together.
 9. The reaction-type vibrator of claim 8,wherein biasing means are affixed to each associated pair of adjustingdials and clutches for biasing said clutch out of engagement with saidadjusting dial, whereby said clutches and said adjusting dials areautomatically disengaged when said locknuts are loosened.
 10. Thereaction-type vibration generator of claim 8, wherein each of saidadjusting dials has a displacement scale affixed to it and each of saidclutches has an index marker affixed to it, said displacement scale andsaid index markers being affixed thereto and calibrated in a fashionsuch that the amplitudE of vibration of said vibration generator can beadjusted by aligning said index markers with corresponding indicia onsaid displacement scales.